Interfacial Engineering: The interlayer interaction in van der Waals materials can be affected by the interlayer stacking sequence or external electric fields. Recent work suggests that electric fields directly modify the electronic band structure of  MnBi\(_2\) Te\(_4\)   instead of via affecting the magnetism[1]}. Stacking configuration may provide an effective and convenient control of the magnetism and hence the topological properties of  MnBi\(_2\) Te\(_4\) . As in other van der Waals magnets, stacking faults in  MnBi\(_2\) Te\(_4\)  may form during materials synthesis, or during mechanical exfoliation or device fabrication. There are ample examples where stacking faults modify the magnetic properties in van der Waals magnets. For example, in RuCl\(_3\) , T\(_N\)  depends on the stacking sequence of RuCl\(_3\)  layers[2]}; in CrI\(_3\) , where ferromagnetism survives in monolayer, the layer stacking leads to antiferromagnetism in bilayer and different ferromagnetic states in trilayer[3]}; in Fe\(_5\) GeTe\(_2\) , an itinerant exfoliable ferrromagnet, partial substitution of Fe by Co changes the stacking of the building blocks and thus the magnetic properties[4]}. Figure REF  shows our preliminary results that demonstrate that stacking faults suppress T\(_N\)  and this indicates that controlling the lateral stacking might eventually lead to a ferromagnetic interlayer coupling that would facilitate the observation of QAHE. More theoretical and experimental efforts are needed to precisely manipulate the lateral sliding of SLs and to understand the corresponding modification of magnetic and topological properties. Twisting the SLs provides a different approach to manipulate the stacking. A recent theoretical study on twisted bi-SL  MnBi\(_2\) Te\(_4\)  moire superlattice suggests that the twisted stacking facilitates the emergence of QAHE in addition to other possible correlated topological phases[5]}.
